Varicella-zoster virus (VZV), the causative agent of chicken pox (varicella) and shingles (zoster), shares with other herpesviruses the ability to cause both productive infections as well as to enter a latent state. Reactivations of VZV to give zoster are most common among elderly and imunosuppressed patients (especially AIDS patients), and disseminated zoster can be life-threatening for these patients. A common complication of zoster, especially in the elderly, is post-herpetic neuralgia, characterized by dermatomal pain persisting for months or years following the zoster rash. Studies of VZV have been hampered because the cell-associated nature of the virus results in low-titer cell-free virus and an absence of viral mutants, and because no good animal model systems exist. The complete DNA sequence of VZV does permit deductions of probable gene function by comparison with the better-studied Herpes simplex virus (HSV), deductions which can be tested experimentally. In productive infections, and in reactivation from latency, the Immediate Early (IE) proteins of HSV, particularly the ICP4 (Vmwl75) protein, are critical for the cascade gene expression. The function of the VZV IE gene 62 (140K, ORF62) protein will be compared with ICP4 to assess similarities, as well as differences which may explain differences in pathogenesis. Cloned VZV genes will be used to determine how VZV 140K trans-activates gene expression. Transient co-transfection assays with wild-type and mutant VZV promoters of different kinetic classes will determine whether VZV 140K can trans-activate gene expression in a sequence-specific manner. The specificity of the DNA binding domain of VZV 140K will be pursued in detail, first using a bacterially-expressed 230 amino acid domain of gene 62, and later using extracts of VZV-infected cells containing native 140K protein. Gel retardation and DNaseI footprinting assays will use fragments of viral promoters and synthetic deoxyoligonucleotides as targets. VZV 140K will also be tested for its ability to form specific complexes with cellular proteins. These molecular biological studies of the functioning of a critical VZV regulatory protein are a prelude to future studies of the specific regulation of VZV gene expression in permissive cells and in nonpermissive cells (latency conditions), as part of long-range goals of understanding the biology of this human pathogen.